Principles of interconnect settlement

This document is a design how OSB handles interconnect agreements based on the requirements of Telikom PNG.
It also describes what functionality has been added to the library to efficiently support these agreements.

Interconnect Settlement bases on a mutual agreement between two partner networks that states the terms and conditions for each party to use his partner's network services. The basic principles applied by the two parties A and B of such an agreement generally are as follows:

Diagram I: Simple interconnect scenario from PNG Telikom's point of view

Components of the OSB Settlement System

Essentially, the OSB settlement system combines OSB mediation and rating with OSB billing. The diagram below shows a simplified view of the settlement usage data flow. It doesn't show party analysis, storage, record filtering and recycling.

Diagram II: Simplified settlement usage data flow

Existing OSB concepts will be used for interconnect settlement, some of which will need to be specialized and/or extended for settlement purposes.

Usage collection and Mediation

Usage collection is the process of collecting usage records from a given usage record source, e.g., a switch, and making them available in a usage record stream. In order to make the system self-sufficient in case of data loss or corruption during processing, the records should be stored in persistent storage (files) immediately after they are collected from the usage record source. The records enter the call accounting chain when they are read from these files.

Mediation can be broken down into conversion, filtering, aggregation (partial call record assembly) and (possibly) duplicate checking.

Telikom PNG requirements

Call Accounting

For each report sent to the partner carrier, it must be possible to identify the related call records. This should be a side-effect of the call accounting.

Call accounting: should also allow for a comparison between what was charged to subscribers and what external carriers asked for (margin analysis).

Telikom PNG requirements

Party analysis and rating

For settlement purposes, the involved parties (interconnect partners) are generally identified from the trunk information in the records. This information must be available in call records generated by the gateway switch. Special cases include a call on an outgoing trunk which must be charged instead of reconciled (and not a negative charge to be calculated). See the Rating Usage Scenarios document for a comprehensive discussion.

Interconnect rating is the rating of calls for interconnect settlement and reconciliation. For settlement, call records of incoming calls from each partner are rated and for reconciliation, call records of outgoing calls to each partner are used.

Re-rating of calls is required. In a post-paid scenario this means that calls which are rejected by the rating engine are isolated and can be recycled at a later time (multipe cycles should be possible).

Telikom PNG requirements


In a settlement system, in contrast to a postpaid retail billing system, we typically process only very few invoices, each of which is created from (potentially) millions of callrecords.

In order to relieve the interconnect billing engine, storage creates and maintains "summary usage records" (SRs) in a dedicated table. Billing does not have to read the individual usage records, it only reads SRs. This means that the summary records need to contain enough detail info so that billing can still apply discounts on the final invoices. There should be one SR for each tupel of <agreement, rating info, etc> and a given time period (typically 1 day - this determines the finest resolution for billing).

In really big systems, it may be necessary to store usage records in different tables (even databases?) dependent on the agreement.

Extraction ("reverse storage"): It should be possible to extract callrecords from the system and convert them to ASN.1 format (e.g., CDR files to send to the partner).


It should be possible to start the billing engine for a single contract and/or contract owner (interconnect carrier). Settlement billing uses only the summary records to avoid having to process millions of records for each agreement at the end of the month.

It should be possible to generate intermediate reports for the agreements. Such intermediate statements can be generated for any time period. Typically, intermediate statements are generated every month and the invoice is created every quarter.

Invoice and reconciliation statements differ in that each summary usage record must be on exactly one invoice but reconciliation reports and intermediate statements can be created for any given time period (including multiple reports for one period, reports for overlapping time periods and gaps between reporting periods).

For certain requirements it is necessary that billing re-rates the calls. This is the case to, e.g., compute charges based on the total number of minutes accrued in the billing interval.

It should be possible to apply promotions on the summary records.

The following XML documents need to be generated:

Preliminary thoughts about the modeling of a settlement agreement:

Model 1: One product containing INTRUNK resource and OUTTRUNK resource, one tariff system and relevant services. The result is a combined statement containing sections for both, settlement as well as reconciliation. This model can be used for a bilateral invoice in one direction only, with netting of traffic.

Model 2: Two products. One with INTRUNK resource, tariffsystem for invoice and relevant services and one with OUTTRUNK resource, tariffsystem for reconciliation and relevant services. Both products can be assigned to one contract or to two different contracts. If the products are assigned to the same contract, then the result is very similar to model 1. On the other hand, if the products are assigned to two different contracts then it is possible to generate settlement and reconciliation statements individually.

Telikom PNG requirements

Agreement admin

View/create/modify/delete agreement

Network admin

Configuration of network elements (e.g., trunks).


The settlement system should be able to produce a number of standard reports. The following list describes each standard report briefly.

Carrier summary reports

Account status reports

Operations reports

Tariff system related (pricing structure) reports